package nine.test_9_26;

import java.util.Scanner;

public class TestMain1 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        long n = scanner.nextLong();
        if(n % 2 == 0) {
            System.out.println((n / 2) * (n / 2));
        } else {
            System.out.println((n / 2) * (n / 2 + 1));
        }
    }
}
